Based on historical comparisons among master-pupil chains and other aspects of social networks among philosophers, some prmciples are suggested regarding long-term intellectual change. The higher the eminence ofphilosophers, the more tightly they are connected to mtergenerational chains of other eminent philosophers, and to horizontal circles of the intellectual community. Intellectual creativity proceeds through the contemporaneous development of rival positions, dividing up the available attention space in the intellectual community. Strong thought-communities, those that have strong external support for their institutional base, (...) subdivide to maximize internal distinctiveness; weakly supported thought-communities disappear or amalgamate by syncretism. External conditions thus affect the content of ideas indirectly by affecting the space available in the mternal field of the intellectual community. The content of philosophies, the degree of abstraction and self-conscious reflection upon intellectual operations, depends on how many generations intellectual networks maintain continuity under conditions of creative rivalry. New positions are produced by competitive appropriation of prior ideas and by negation of preexisting positions along the lines of greatest organizational rivalry. (shrink)